1. Field of the Invention
A method of producing a self aligning concrete pipe to improve the seal of the joint cooperatively formed between adjacent concrete pipes.
2. Description of the Prior Art
Concrete pipe of various sizes, shapes and lengths are widely used to transport or carry large volumes of water or other fluids. A primary problem has always been to secure dependable joints that prevent exfiltration and/or infiltration of fluids and sand or dirt particles.
An equally significant problem is the manufacture and assembly of concrete pipes and particularly oval concrete pipes axial, vertical and horizontal misalignment of adjacent concrete pipes during assembly.
The most simple, common and predominant joint is known as a T&G joint, consisting of a male member called a tongue and a female member called a groove, along with various resilient retaining or sealing rings/gaskets. Henceforth, in the following illustrations and descriptions of prior art and my invention, the three elements involved will for the sake of brevity and clarity be referred to as "tongue", "groove", and "gasket".
A different configuration of the groove in which the groove end is enlarged on the outside for additional strength, will be referred to as a "bell".
T&G joints are generally of two types. In the first type the walls of the tongues and grooves are slightly contoured for receiving different compatible configurations of gaskets.
The second type is similar with one exception, in that there is a recess in the wall of the tongue for receiving and containing an annular O ring which is about 15% smaller in diameter than the recess, and has to be stretched and shaped into place in the groove.
The first type of T&G joint has generally been superseded by the second type, because of the difficulty in manipulating, aligning and joining the T&G of the adjacent pipes, in a trench under adverse conditions, without mutilating or displacing the gasket.
The second type of T&G Joint, with a recess, has a lip forward of the recess that generally protects O ring or similar snap-in-gasket, against mutilation or displacement during joining.
This lip makes it possible to partially join the tongue and groove with concrete to concrete contact before the outer edge to the groove makes contact with the O ring or similar gasket in the recess of the tongue.
Extreme care (not always used) and extra time and labor is required to make sure that the O ring is uniformly stretched after being shaped in place on the recess of the tongue so as to maintain a uniform diameter, the lack of which could lead to snagging or insufficient pressure on one radial section of the groove resulting in a leaky joint.
However, since the diameter of the O ring is approximately twice the diameter of the depth of the recess, such O rings are still subject to being snagged or sheared or displaced by the leading edge of the groove if said leading edge fails to slip over the O ring in the recess during joining.
As a result of the extreme pressure required to seal a narrow radial section of the groove, it is necessary to enlarge the groove end, forming a bell to obtain the necessary strength to keep the groove from breaking out. The tongue is under compression and the groove is under tension and concrete has high compressive strength but rather low tensile strength.
The bell itself is costly and undersirable because:
the bell on the pipe requires a more expensive and complicated form, the bell also requires larger and heavier and more expensive pallets, the bell requires additional concrete; PA0 the protruding bell makes loading and hauling to job site more difficult; PA0 where the terrain is very low and the pipe has to be installed close to ground level, a deeper trench is required; and PA0 after the bed in the bottom of the trench has been contoured to the specified slope, the bed then requires additional excavating to accommodate the protruding bell.
All of these add to the costs by requiring more expensive equipment with additional time and labor.
Prior art is shown in U.S. Pat. Nos. 2,809,853; 2,832,614; 3,315,971; 3,414,273; 3,515,396; 3,520,541; 3,573,871; 3,575,430; 3,656,771; 3,675,685; 3,857,589; 4,084,828; 4,174,859; 4,279,425; together with Germany No. 2,402,022 and Great Britain No. 1,080,816